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Discussion Starter · #1 ·
Hey guys - I wanted to get some opinions as to whether this is worth my time or not to mess with:

I'm building my '65 mustang, currently swapped in an 8 inch. Well, as time goes by and the build progesses, things are changing. I've been toying with the idea of "sometime in the future" swapping in a nine inch rear. Well, it just so happens that I found a deal on a nine inch rear from a guy thats got a bunch of mustang parts he's selling. So here's what I need opinions on:

My build is a 5.0 block with roller components, T5 transmission, novi supercharger, and soon to be purchased blower cam (comp cams), upgraded valve springs/locks to match everything, and the eventual plan to open up the breathing of the engine with upgraded heads, MSD ignition, edelbrock performer intake, holley 650 double pumper.

I've read up a bunch about going beyond stock engine-wise using an 8 inch and I've seen both sides of the fence - most say that with a properly built 8 inch it will be fine, the other half I've read say that the 8 is something that can get stressed past it's breaking point.

So my dilemma right now is to go ahead and build out my 8 with 3.80 gears and an auburn unit and leave it alone, or get this guy's nine and spend the money building that one up. It's out of a bronco so the little I've read up on it is that it's 5x5.5 lugs and a bunch of little stuff that'll need to be changed to make it work.

Is this 9 worth my time or am I fine using my 8 and building it out?
 

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depends.if the 9 already has gears that will work for you...go with that..if its an LS, even better
 

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Rebuld the 8. 9 are great everyone wants them but, if you rebuild and put a posi in the 8 it will be great too. The nine is stronger and can handle more torqe. I have two 9's and i'm still going to keep my eight. I have a 302 H.O. f 303 roller cam, victor Jr heads and intake, harpland roller rockers, 750 eld carb electric water pump. Bulit myself. I have not dyno but should have 400hp+ to the wheels
 

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I believe i know which 9 inch you were looking at. It was on craigslist for about 2 days then someone bought it. Was 500 bucks for a 9 inch limited slip with 3.25 gears. I was about to buy it too :shigrin
Mustang kilgore, if you have a 9 inch available to you, you should probably use that if you plan on big power like that. 8 inchers are a good rear but once you get over 300 to the wheels go to a 9. Although to be realistic i doubt you will have that much power without stroking it out. 450 horse is pretty ridiculous on an f cam but prove me wrong!:bigthumbsup
 

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Discussion Starter · #5 ·
Well see that's kind of my debate. I don't really know what numbers to expect yet to the wheels from my setup, so I don't want to dump money into the wrong axle. The 9 looks like I'll have to do what I planned to do to the 8 (gear swap and auburn unit), and the addition of either having the bolt pattern changed over to 5x4.5 or getting new axles for it. I just don't know what the strength limit is on an 8 and don't want to push past stock horsepower numbers and break it. I like the idea of the 9 being virtually indestructible. Like mustangkilgore said though, they're great and everybody wants one, I just don't want to sell this idea to myself when it might be overkill.

Basically, I would want to do all this out of necessity, not out of "hey, look what I put under there" because I can.

Soo...what would you do?
 

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I"m just rebuilding my 8 with 3.25 gears and traction-loc. I figured if my 8 is good enough to hold up to 400 hp which I'm hauling about 340 or so, then I'll just throw those things in instead of going for the ford 9".
 

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Hey sdmustangrider, how are you gonna go about rebuilding yours? I have about 340hp too and im debating on how i will go about my rear end build also.
 

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Discussion Starter · #9 ·
Yes, actually. My only drawback is I didn't really want to have to get into welding spring perches on and whatnot. I realize that both the 8.8 and the 9's have tons of aftermarket stuff to choose from, the 8 seems to have been left out in the cold. My 7.5 I have leaned up in my garage looks like a toothpick compared to this stuff.
 

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To answer your question, if you are thinking about a paxton novi, then definately go for the 9 inch. Considering you will already have a decent engine with over 300 hp N/A, adding a paxton will require a 9 inch. I wouldnt go cheap on a quality build which this one seems like. And by the way, a 9 inch will probably cost around the same as rebuilding your 8 inch the way you would want anyways.
 

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I have two rearend from a 59 ford pick-up. The other a 72-79 ford of some type. I will sell pickup only. AZ.

Take a look at the engine its a 400+. The Victor jr heads are 500hp to stock geometry. If you rebuild the 8 it will hold that. If you have to much torqe with 400+ go 9in.
 

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Hey sdmustangrider, how are you gonna go about rebuilding yours? I have about 340hp too and im debating on how i will go about my rear end build also.

The guy who built my engine, he's a big time mechanic for races around the country. What I'm doing is going to buy the trac-loc and 3.25 gears with new bearings for it and just install them. Your 8 should be good enough to hold 340hp. For me keeping the 8, maybe sometime in the future when I decided to kick some more hp into my car, I might switch over to a 9. If it holds the power, I don't need to swap anything out.
 

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How much do you think it will cost you if you dont mind me asking? I basically want the same thing, 3.25's and limited slip too haha. I probably have a friend that can help me out with it too. Alcohol dragster mechanic haha. Hopefully he can help me out too.
 

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How much do you think it will cost you if you dont mind me asking? I basically want the same thing, 3.25's and limited slip too haha. I probably have a friend that can help me out with it too. Alcohol dragster mechanic haha. Hopefully he can help me out too.

Definitely if your friend knows how to do it, you're golden. As for having my mechanic doing it, he charges $300 to install. I called a couple shops and got the 450-500 price but my mechanic will charge under the table without tax. As for parts, and because ford 8 parts are not common, you'll see prices are freakin expensive, as oppose to ford 8.8. But for 3.25 gears, they go about $158 and up. I found a guy on ebay who had 3.40 gears for $80 bucks. Trac loc you'll find on Ebay for about $340. I'm going to call a shop up first here in SD and see what they have. Might be able to pay for it cheaper but who knows. And Master bearing for rearend goes about $100-150 which is a MUST when swapping out gears. I'll send you a couple links on people who are selling. Check Summit too. Might find a good price if there is a Summit brand.
 

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I would ask tire size and compound? Chances are you'll break traction before the rear. Unless you've got some stickies on there.
 

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Discussion Starter · #17 ·
I would ask tire size and compound? Chances are you'll break traction before the rear. Unless you've got some stickies on there.
Hey rodbender, if you're asking me this question as we seem to have two or three conversations going on in this thread at this point, I'll be using 17's of some variety - the exact size will be determined when I mock up the wheels and measure for fitment so I don't end up with tire rub. No stickies for me lol.

Turns out, actually, that I talked to the guy who had the nine he was selling and it was a later model truck axle. It would have bolted right in, but the slight problem would have been the tires sticking out from under my car four inches on each side. No big deal, right? Had it been the early truck axle, the track width difference would have only been 3/4 of an inch which could have been taken care of with properly backspaced wheels.

For now, the eight is staying. Once I get a little more money together I'm going to finish out my build, including the axle. I'm talking with another guy at this point that has a nine that is the correct track width for my car, so I'm thinking about just picking that one up and putting it aside until the money comes in to build it. My main question of starting this thread was when I get ready to spend money upgrading rears, should I put the money into buying an auburn unit and gears plus shop time to swap the stuff in my eight, or if I found a good deal on a nine, spend the money buying nine inch stuff and not have to worry about the ongoing debate of how much horsepower, torque and stress the axle's going to have to put up with. I'd rather spend the money once, not twice if I ever thought about upgrading to a nine.
 
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